1. Field of the Invention
The present invention relates to a vehicle air conditioner that prevents a windshield from fogging as appropriate and maintains comfortable feelings of a driver and a passenger.
2. Description of Related Art
In a vehicle air conditioner, some techniques are used for preventing a windshield from fogging. U.S. Pat. No. 5,931,006 discloses one example. In the U.S. patent, when a blowout air temperature toward the windshield at a defroster (DEF) blowout port is lower than a dew point temperature of the outside air, air blowing toward the windshield is stopped to prevent an outside of the windshield from fogging in a cooling mode.
However, the blowout air temperature at a defroster blowout port is usually lower than a windshield temperature in the cooling mode. Accordingly, in the example, it is determined more than necessary that the windshield fogging occurs because the windshield fogging is determined based on a comparison between the blowout air temperature and the dew point temperature. As a result, air blowing toward the windshield may be stopped well before the windshield fogs, and air volume may be decreased more than necessary.
JP-A-2002-120545 discloses another example. In this disclosure, when a capability for dehumidifying and preventing a fogging is low, air blowing from the DEF blowout port is increased or air temperature is increased to prevent an inside of the windshield from fogging in a heating mode.
However, in the later example, air volume blowing from a FOOT blowout port is decreased because a part of warm air is used for blowing from the DEF blowout port to warm the windshield. As a result, heating power may be decreased as a whole.